ABSTRACT: Methamphetamine (METH), an addictive stimulant has long lasting toxic effects on the central nervous system (CNS). Clinical studies indicated that METH dependence has an additive effect on neuropsychological deficits associated with HIV-1 infection. Oxidative stress, excitotoxicity, BBB impairment and glial cell activation, all have been independently implicated in the mechanisms of METH- and HIV-1-associated neurotoxicity. This proposal will investigate specific mechanisms operative in HIV-1 CNS infection and METH abuse that lead to an overall increase in oxidative stress and NF-kB signaling resulting in impairment of astrocytes and endothelial cell function. We propose that METH-mediated oxidative stress in astrocytes leads to a down regulation exitotoxic amino acid transporter (EAAT) -2, the primary astrocyte glutamate scavenger, while in endothelial cells, such an increase in oxidative stress results in loss of BBB integrity. Indeed, our preliminary data suggest that METH exposure caused ROS generation in astrocytes and human primary BMVEC, diminished EAAT-2 expression, in astrocytes, decreased BBB integrity in vitro that was restored by antioxidant treatment, caused decreased expression/re-distribution of tight junction proteins, enhanced adhesion and migration of monocytes across endothelial monolayers and activated small GTPases in BMVEC that were previously implicated in the BBB injury during HIV-1 encephalitis (HIVE). New preliminary data demonstrated increased permeability of BBB in vivo in animals exposed to METH that was prevented by antioxidant treatment. This proposal will investigate a novel concept of mechanistic commonality, i.e. METH-mediated oxidative stress exerts its cell-specific effects in astrocytes and endothelial cells aggravating injury caused by HIV-1 CNS infection and delineate therapeutic options for these targets using in vivo studies. Using a combination of in vitro assays and METH/HIVE animal model, we will address the following questions: What is the role(s) of enhanced reactive oxygen species, ROS production and NF-kB signaling in diminished expression/function of EAAT-2 in astrocytes? (Aim 1) What are underlying mechanisms of BBB dysfunction and enhanced monocyte adhesion/migration across brain endothelium (via oxidative stress, interference with NF-kB and GTPase signaling)? (Aim 2); and Can therapeutics decreasing oxidative stress and normalizing EAAT-2 function ameliorate BBB dysfunction and neurotoxicity in an animal model for HIVE and METH abuse? (Aim 3) We will address these questions utilizing primary human astrocytes and brain microvascular cells, in vitro BBB models and evaluate combined effects of METH and HIV-1 relevant stimuli on EAAT-2 and BBB function. Antioxidants and specific signaling inhibitors will be utilized to delineate pathways involved in these effects. Our HIVE animal model will be employed to investigate the biological outcomes of these cell-specific mechanisms in cognitive function, BBB damage and neurotoxicity. We believe that the proposed works are highly significant, as they will uncover novel mechanisms involved in the combined effects of HIV-1 and METH in the CNS and propose therapeutic approaches based on these investigations.